OLED multicolor displays

ABSTRACT

An OLED display having at least first, second, and third differently colored pixels includes a first light emitting layer provided over a substrate for the first and second pixels and a second light emitting layer provided over the substrate for the first, second, and third pixels, wherein the first and second light emitting layers produce light having different spectra, and wherein the light produced by overlapping the first and second light emitting layers has substantial spectral components corresponding to the light output desired for the first and second pixels, and the light produced by the second light emitting layer has substantial spectral components corresponding to the light output desired for the third pixel; and first and second color filters in operative relationship with the first and second pixels.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly assigned U.S. patent application Ser. No.11/050,162 filed Feb. 3, 2005 by Dustin L. Winters, et al., entitled“Making Multicolor OLED Displays”, and commonly assigned U.S. patentapplication Ser. No. 11/113,915 filed concurrently herewith by JeffreyP. Spindler, entitled “Multicolor OLED Displays”, the disclosures ofwhich are herein incorporated by reference.

FIELD OF INVENTION

The present invention relates to organic light emitting diode (OLED)displays. More specifically, this invention relates to multicolor OLEDdisplays having three or more pixels with improved power efficiency.

BACKGROUND OF THE INVENTION

Color, digital image display devices based on organic light emittingdiodes (OLED) are well known. In the simplest form, an OLED is comprisedof an anode for hole injection, a cathode for electron injection, and anorganic media sandwiched between these electrodes to support chargerecombination that yields emission of light. In order to construct anOLED display, a plurality of individually addressable OLED elements arearranged in a matrix of pixels. Each pixel includes an independentlyaddressable OLED and is capable of producing light. Such matrixes can beof the passive type where electroluminescent OLED layers are sandwichedbetween two sets of orthogonal electrodes (rows and columns). An exampleof a passive matrix driven OLED display device is described in U.S. Pat.No. 5,276,380. Alternately, the OLED display can be constructed of theactive matrix type where one or more circuit elements, such as atransistor or capacitor, is used to drive each OLED. An example of anactive matrix driven OLED display device is described in U.S. Pat. No.5,550,066.

In order to construct a multicolor display, the pixels are arranged toproduce a variety of colors. For example, a multicolor display can beconstructed to have red, green, and blue pixels. Such a display isreferred to as an RGB display. Additional colors can be achieved by sucha display by mixing the light emitted by the red, green, and bluesubpixels in various ratios.

However, the human eye is less sensitive to light emitted by the redpixels or the blue pixels compared to light emitted by the green pixels.As such, the red and blue pixels need to emit more light to achieve thedesired brightness compared to the green pixels. This causes the displayto consume a large amount of power.

Other displays, such as described in U.S. Pat. No. 6,693,611, havingadditional pixels, which emit colors between that of the green, and thered pixels or between that of the blue and green pixels have beenproposed. These additional pixels emit light having a color to which thehuman eye is more sensitive compared to either the red pixels or theblue pixels. As such, one or more of these additional pixels can becombined with one or more of the other pixels to produce mixed colors,such as a white color. The resulting display can produce such mixedcolors at a lower power consumption compared to a comparable RGBdisplay.

One approach to constructing such a display having four or moredifferently colored pixels, as discussed in U.S. Pat. No. 6,693,611, isto provide separate OLED electroluminescent layers for each of thepixels. This results in the need to pattern one or more of the OLEDelectroluminescent layers such that it is precisely aligned with thedesired pixel. Several methods of patterning OLED layers are known inthe art. For example, OLED layers can be deposited through a shadow maskin order to selectively deposit only in the desired areas. Shadow masksshould then be aligned with the target pixel. Such alignment processes,however, are more complicated and can slow manufacturing throughput.Furthermore, the accuracy of the alignment of the shadow mask to thesubstrate tends to be poor, thereby requiring large tolerances for thepatterned layers resulting in wasted surface area of the display. Shadowmasks also tend to cause damage to the OLED pixels when the maskcontacts the display substrate. Alternate methods of separatelypatterning OLED layers for each layer are also known. For example, amethod of pattering the OLED layers by transferring the OLED materialfrom a donor sheet by use of a laser is known. However, this methodrequires the use of consumable donor substrates and complex laserwriting equipment. The process of writing each pixel with a laser canalso reduce manufacturing throughput. Another example process forpatterning OLED layers involves deposition of the OLED materialsdissolved in a solvent as droplets by way of an ink jet print head. Thismethod requires the precision placement of the ink jet droplets. Assuch, complex structures for controlling droplet placement and spreadcan be required and tolerances for the pixel area can be large.

SUMMARY OF THE INVENTION

It is an object of the present invention to avoid the above mentionedproblems and provide a multicolor OLED display with improved powerefficiency that reduces the need for precisely patterning one or more ofthe OLED layers.

This object is achieved by an OLED display having at least first,second, and third differently colored pixels, comprising:

a) a first light emitting layer provided over a substrate for the firstand second pixels and a second light emitting layer provided over thesubstrate for the first, second, and third pixels, wherein the first andsecond light emitting layers produce light having different spectra, andwherein the light produced by overlapping the first and second lightemitting layers has substantial spectral components corresponding to thelight output desired for the first and second pixels, and the lightproduced by the second light emitting layer has substantial spectralcomponents corresponding to the light output desired for the thirdpixel; and

b) first and second color filters in operative relationship with thefirst and second pixels.

ADVANTAGES

The present invention provides a multicolor OLED display having at leastthree different color pixels that can be made more effectively.

Because of the organization of the design of the multicolor OLEDdisplay, simplified manufacturing steps can be used with fewer precisealignments or patterning steps.

A feature of the present invention is that multicolor OLED displays madein accordance with the present invention can provide improved powerefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a multicolor OLED display having three differently coloredpixels;

FIG. 2 shows a top side view of a pixel according to the firstembodiment of the present invention;

FIG. 3 shows a cross section view of a group of pixels taken along theline 3-3′ of FIG. 2;

FIG. 4 shows a top side view of a pixel according to the secondembodiment of the present invention;

FIG. 5 shows a cross section view of a group of pixels taken along theline 5-5′ of FIG. 4;

FIG. 6 shows a multicolor OLED display having four differently coloredpixels;

FIG. 7 shows a top side view of a pixel according to the thirdembodiment of the present invention;

FIG. 8 shows a cross section view of a group of pixels taken along theline 8-8′ of FIG. 7;

FIG. 9 shows a multicolor OLED display having five differently coloredpixels;

FIG. 10 shows a top side view of a pixel according to the fourthembodiment of the present invention;

FIG. 11 shows a cross section view of a group of pixels taken along theline 11-11′ of FIG. 10; and

FIG. 12 shows the EL Spectra for OLED devices of Examples 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example of a multicolor OLED display including threepixels that produce different colored light emission. For example, pixel11 a preferably produces red light, pixel 11 b preferably produces greenlight, and pixel 11 c preferably produces blue light. These pixels canbe arranged in groups, such as pixel group 10. Although it is shown thateach pixel group includes each of the differently colored pixels, thepresent invention is not limited to this case. Instead, some coloredpixels can be present in greater number than other colored pixels.

FIG. 2 shows a top side view of pixels 11 a, 11 b, and 11 c according tothe first embodiment of the present invention. In a passive matrixconfiguration, these pixels can be addressed by providing a matrix oforthogonal electrodes such as first electrodes 110 a, 110 b, and 110 cand second electrode 130. That is, pixel 11 a is constructed from firstelectrode 110 a and second electrode 130, pixel 11 b is constructed fromfirst electrode 110 b and second electrode 130, and pixel 11 c isconstructed from first electrode 110 c and second electrode 130. In thisconfiguration, all pixels in a column share the same first electrode andall pixels in a row share the same second electrode. As such, thesepixels are arranged into a stripe pattern. However, the presentinvention is not limited to this arrangement and other arrangements suchas delta pattern arrangements and quad arrangements can be applied byone skilled in the art. Furthermore, the present invention is notlimited to the passive matrix configuration and an active matrix drivingscheme can be applied by one skilled in the art.

According to the present invention, light emitting layer 123 a isprovided for pixels 11 a and 11 b so as to be common between both ofthese pixels. This requires light emitting layer 123 a to be preciselyaligned or patterned to these pixels. Light emitting layer 123 c isprovided for pixels 11 a, 11 b, and 11 c and is common to all pixels,thus requiring no patterning step. In this manner, the number ofprecision aligned depositions required to form these three differentlycolored pixels is reduced from three to one. Light emitting layer 123 acan be formed from a single step, such as for example, depositionthrough a single shadow mask, precise placement of one or more dropletsfrom the same ink jet head, or transfer from the same donor sheet. Assuch, this layer can be continuously formed between pixels 11 a and 11 bas shown. This can be achieved, for example, by using a single openingin the shadow mask to deposit the entire layer. Similarly, lightemitting layer 123 c can be formed from a single source. Such acontinuous arrangement is preferred to reduce surface area allocated foralignment tolerances in the manufacturing process. To facilitate such acontinuous arrangement, the pixels, which share the same light emittinglayer, are preferably disposed to be adjacent to one and other. Forexample, pixel 11 a is adjacent to pixel 11 b as shown.

Light emitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between red and green, otherwisereferred to as yellow-orange. Light emitting layer 123 a is arranged soas to produce light having spectral components corresponding to thedesired colors of both pixel 11 a and pixel 11 b. This can be achievedby forming a light emitting layer of materials that emit a wide spectrumof light in the red, red-orange, orange, yellow-orange, yellow,yellow-green, and green wavelengths. Similarly, light emitting layer 123c is preferably arranged to emit light having a spectrum correspondingto a blue color. Light emitting layer 123 c is arranged so as to producelight having spectral components corresponding to the desired color ofpixel 11 c. Although light emitting layers 123 a and 123 c areoverlapped for pixels 11 a and 11 b, the combination of light emittinglayers 123 a and 123 c is arranged so as to produce light having mostlyspectral components corresponding to the desired colors of both pixels11 a and 11 b. In order to achieve the red color desired for pixel 11 a,color filter 140 a is formed in the path of the light emission, or inoperative relationship, in pixel 11 a to absorb undesired spectralcomponents for pixel 11 a and pass the desired spectral componentscorresponding to the desired red color. Color filter 140 a can beconstructed, for example, to transmit red light and absorb light havinglower wavelengths. In order to achieve the green color desired for pixel11 b, color filter 140 b is formed in operative relationship, that is,at least partially in the path of the light emission between the pixeland the viewer, in pixel 11 b to absorb undesired spectral componentsfor pixel 11 b and pass the desired spectral components corresponding tothe desired a green color. That is, color filter 140 b can beconstructed, for example, to transmit green light and absorb lighthaving different wavelengths. The blue color desired for pixel 11 c canbe achieved with or without the use of a color filter.

An alternate three pixel embodiment can be achieved by providing a firstpixel emitting blue light, a second pixel emitting green light, a thirdpixel emitting red light. In this alternate embodiment case, the firstlight emitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between blue and green, otherwisereferred to as blue-green. Light emitting layer 123 a is arranged so asto produce light having spectral components corresponding to the desiredcolors of both pixel 11 a and pixel 11 b. This can be achieved byforming a light emitting layer of materials that emit a wide spectrum oflight in the blue, blue-green, green-blue and green wavelengths.Similarly, light emitting layer 123 c is preferably arranged to emitlight having a spectrum corresponding to a red color. Light emittinglayer 123 c is arranged so as to produce light having spectralcomponents corresponding to the desired color of pixel 11 c. Althoughlight emitting layers 123 a and 123 c are overlapped for pixels 11 a and11 b, the combination of light emitting layers 123 a and 123 c isarranged so as to produce light having mostly spectral componentscorresponding to the desired colors of both pixels 11 a and 11 b. Inorder to achieve the blue color desired for pixel 11 a, color filter 140a is formed in the path of the light emission, or in operativerelationship, in pixel 11 a to absorb undesired spectral components forpixel 11 a and pass the desired spectral components corresponding to thedesired blue color. Color filter 140 a can be constructed, for example,to transmit blue light and absorb light having higher wavelengths. Inorder to achieve the green color desired for pixel 11 b, color filter140 b is formed in the path of the light emission, or in operativerelationship, in pixel 11 b to absorb undesired spectral components forpixel 11 b and pass the desired spectral components corresponding to thedesired green color. Color filter 140 b can be constructed, for example,to transmit green light and absorb light having different wavelengths.The red color desired for pixel 11 c can be achieved with or without theuse of a color filter.

FIG. 3 shows a cross sectional view of the device of FIG. 2 taken alongline 3-3′. FIG. 3 shows that pixels 11 a, 11 b, and 11 c produceinternal light emission 220 a, 220 b, and 220 c, respectively. Internallight emission 220 c exits the device without filtration to becomeexternal light emission 210 c. Internal light emission 220 a passesthrough color filter 140 a prior to exiting the device resulting inexternal light emission 210 a. Similarly, internal light emission 220 bpasses through color filter 140 b prior to exiting the device resultingin external light emission 210 b. Color filters 140 a and 140 b arepreferably organic layers deposited by lamination or spin coatingmethods known in the art. The color filters are preferablyphoto-patternable as is known in the art wherein the color filtermaterials are deposited over the entire display surface, exposed with alight source, and either the exposed or the unexposed regions areremoved by use of a solvent. This method provides effective alignmentaccuracy to the desired pixel region. However, the present invention isnot limited to this preferred case, and other ways of depositing andpatterning the color filter material as are known in the art can beemployed by one skilled in the art. Furthermore, additional black matrixstructures (not shown) which absorb some portion of all visible lightcan optionally be disposed in the non-emitting regions between pixels toreduce ambient light reflection and improve display contrast as is knownin the art.

The pixels are constructed over substrate 100. Light can exit the deviceby passing through substrate 100 as shown. Such a configuration is knownas a bottom emitting device. Substrate 100 should be constructed of atransparent material such as glass or plastic. Alternately, the devicecan be constructed so that light exits the device in the directionopposite the substrate. Such a configuration is known as a top emittingdevice. The substrate can be selected from materials that are nottransparent such as metals, or semiconductor materials like siliconwafers.

For the case of the bottom emitting device, as shown, first electrodes110 a, 110 b, and 110 c are arranged to transmit light and arepreferably constructed of a conductive transparent material such asindium tin oxide (ITO) or indium zinc oxide (IZO). Second electrode 130is preferably constructed of a reflective conductive material such asaluminum, silver, magnesium silver alloy, or the like. These electrodescan be constructed of a single layer or of multiple layers in order toachieve the desired light absorption or reflection properties andconductivity properties. For the alternate case of a top emittingdevice, it is preferable that the second electrode is transparent andthe first electrode is reflective. A top emitting device, color filters140 a and 140 b would be disposed in the path of the light on the sideof the second electrode. Although the first electrodes are shown asbeing arranged in the column direction and the second electrode is shownas being arranged in the row direction, the opposite arrangement is alsopossible.

FIG. 4 shows a top side view of pixels 11 a, 11 b, and 11 c according tothe second embodiment of the present invention. Light emitting layer 123a is provided for pixels 11 a, 11 b, and 11 c so as to be common betweenall pixels, and therefore does not require a precise alignment orpatterning step. Light emitting layer 123 c is provided for pixel 11 conly, thus requiring a precise alignment or patterning step. In thismanner, the number of precision aligned depositions required to formthese three differently colored pixels is reduced from three to one.Light emitting layers 123 a and 123 c can be formed as previouslydescribed.

Light emitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between red and green, and produceslight having spectral components corresponding to the desired colors ofboth pixel 11 a and pixel 11 b. Similarly, light emitting layer 123 c ispreferably arranged to emit light having a spectrum corresponding to ablue color, and produces light having spectral components correspondingto the desired color of pixel 11 c. Although light emitting layers 123 aand 123 c are overlapped for pixel 11 c, the combination of lightemitting layers 123 a and 123 c is arranged so as to produce lighthaving mostly spectral components corresponding to the desired color ofpixel 11 c. In order to achieve the red color desired for pixel 11 a,color filter 140 a is formed in the path of the light emission, or inoperative relationship, in pixel 11 a to absorb undesired spectralcomponents for pixel 11 a and pass the desired spectral componentscorresponding to the desired red color. In order to achieve the greencolor desired for pixel 11 b, color filter 140 b is formed in the pathof the light emission, or in operative relationship, in pixel 11 b toabsorb undesired spectral components for pixel 11 b and pass the desiredspectral components corresponding to the desired a green color. The bluecolor desired for pixel 11 c can be achieved with or without the use ofa color filter.

Another alternate three pixel embodiment can be achieved by providing afirst pixel emitting blue light, a second pixel emitting green light,and a third pixel emitting red light. In this alternate embodiment case,the first light emitting layer 123 a is preferably arranged to emitlight having a spectrum corresponding to a color between blue and green,and produces light having spectral components corresponding to thedesired colors of both pixel 11 a and pixel 11 b. Similarly, lightemitting layer 123 c is preferably arranged to emit light having aspectrum corresponding to a red color, and produces light havingspectral components corresponding to the desired color of pixel 11 c.Although light emitting layers 123 a and 123 c are overlapped for pixel11 c, the combination of light emitting layers 123 a and 123 c isarranged so as to produce light having mostly spectral componentscorresponding to the desired colors of pixel 11 c. In order to achievethe blue color desired for pixel 11 a, color filter 140 a is formed inthe path of the light emission, or in operative relationship, in pixel11 a to absorb undesired spectral components for pixel 11 a and pass thedesired spectral components corresponding to the desired blue color.Color filter 140 a can be constructed, for example, to transmit bluelight and absorb light having higher wavelengths. In order to achievethe green color desired for pixel 11 b, color filter 140 b can beconstructed, for example, to transmit green light and absorb lighthaving different wavelengths. The red color desired for pixel 11 c canbe achieved with or without the use of a color filter.

FIG. 5 shows a cross sectional view of the device of FIG. 4 taken alongline 5-5′. FIG. 5 shows that pixels 11 a, 11 b, and 11 c produceinternal light emission 220 a, 220 b, and 220 c, respectively. Internallight emission 220 c exits the device without filtration to becomeexternal light emission 210 c. Internal light emission 220 a passesthrough color filter 140 a prior to exiting the device resulting inexternal light emission 210 a. Similarly, internal light emission 220 bpasses through color filter 140 b prior to exiting the device resultingin external light emission 210 b. Color filters 140 a and 140 b arepreferably organic layers as described previously.

The pixels are constructed over substrate 100. Light can exit the deviceby passing through substrate 100 for the case of the bottom emittingdevice, as shown. First electrodes 110 a, 110 b, and 110 c are arrangedto transmit light and are preferably constructed of a conductivetransparent material such as indium tin oxide (ITO) or indium zinc oxide(IZO). Second electrode 130 is preferably constructed of a reflectiveconductive material such as previously described in order to achieve thedesired light absorption or reflection properties and conductivityproperties.

The above embodiments are described as providing three differentlycolored pixels. However, some advantage can be obtained according toalternate embodiments whereby four differently colored pixels areprovided. In FIG. 6 for example, a multicolor display can be constructedaccording to the present invention by providing a first pixel 11 aemitting red light, a second pixel 11 c emitting green light, a thirdpixel 11 d emitting blue light, and a fourth pixel 11 b emitting a colorbetween that of the first and second pixels. As such, a common lightemitting layer would be provided over the first, second and fourthpixels. FIG. 7 shows a top side view of pixels 11 a, 11 b, 11 c, and 11d according to the third embodiment of the present invention. Lightemitting layer 123 a is provided for pixels 11 a, 11 b and 11 c so as tobe common between these pixels, and therefore requires a precisealignment or patterning step. Light emitting layer 123 c is provided forall pixels, and therefore does not require a precise alignment orpatterning step. In this manner, the number of precision aligneddepositions required to form these four differently colored pixels isreduced from four to one. Light emitting layers 123 a and 123 c can beformed as previously described.

Light emitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between red and green, and produceslight having spectral components corresponding to the desired colors ofpixels 11 a, 11 b, and 11 c. Similarly, light emitting layer 123 c ispreferably arranged to emit light having a spectrum corresponding to ablue color, and produces light having spectral components correspondingto the desired color of pixel 11 c. Although light emitting layers 123 aand 123 c are overlapped for pixels 11 a, 11 b, and 11 c, thecombination of light emitting layers 123 a and 123 c is arranged so asto produce light having mostly spectral components corresponding to thedesired color of pixels 11 a, 11 b, and 11 c. In order to achieve thered color desired for pixel 11 a, color filter 140 a is formed in thepath of the light emission in pixel 11 a to absorb undesired spectralcomponents and pass the desired spectral components corresponding to thedesired red color. In order to achieve the green color desired for pixel11 c, color filter 140 c is formed in the path of the light emission inpixel 11 c to absorb undesired spectral components and pass the desiredspectral components corresponding to the desired green color. Thedesired color between red and green for pixel 11 b is achieved withoutthe use of a color filter. The blue color desired for pixel 11 c can beachieved with or without the use of a color filter. A multicolor OLEDdisplay made in this manner can have higher power efficiency. The highefficiency unfiltered wide emission spectrum used in pixel 11 b can beused frequently to replace either the lower efficiency red or greenpixels to produce within gamut colors, as is known in the art.Efficiency can be measured for example in candelas (cd) per ampere (A)of current. As such high efficiency light emission results in displaysthat consume less power, or in other words, have high power efficiency.

Another alternate four pixel embodiment can be achieved by providing afirst pixel 11 a emitting blue light, a second pixel 11 c emitting greenlight, a third pixel 11 d emitting red light, and a fourth pixel 11 bemitting a color between that of the first and second pixels. Lightemitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between blue and green, and produceslight having spectral components corresponding to the desired colors ofpixels 11 a, 11 b, and 11 c. Similarly, light emitting layer 123 c ispreferably arranged to emit light having a spectrum corresponding to ared color, and produces light having spectral components correspondingto the desired color of pixel 11 d. Although light emitting layers 123 aand 123 c are overlapped for pixels 11 a, 11 b, and 11 c, thecombination of light emitting layers 123 a and 123 c is arranged so asto produce light having mostly spectral components corresponding to thedesired color of pixels 11 a, 11 b, and 11 c. In order to achieve theblue color desired for pixel 11 a, color filter 140 a is formed in thepath of the light emission in pixel 11 a to absorb undesired spectralcomponents and pass the desired spectral components corresponding to thedesired blue color. In order to achieve the green color desired forpixel 11 c, color filter 140 c is formed in the path of the lightemission in pixel 11 c to absorb undesired spectral components and passthe desired spectral components corresponding to the desired greencolor. The desired color between blue and green for pixel 11 b isachieved without the use of a color filter. The red color desired forpixel 11 d can be achieved with or without the use of a color filter. Amulticolor OLED display made in this manner can have higher powerefficiency. The high efficiency unfiltered wide emission spectrum usedin pixel 11 b can be used frequently to replace either the lowerefficiency blue or green pixels to produce within gamut colors, as isknown in the art.

FIG. 8 shows a cross sectional view of the device of FIG. 7 taken alongline 8-8′. FIG. 8 shows that pixels 11 a, 11 b, 11 c, and 11 d produceinternal light emission 220 a, 220 b, 220 c, and 220 d, respectively.Internal light emission 220 b and 220 d exit the device withoutfiltration to become external light emission 210 b and 210 d,respectively. Internal light emission 220 a passes through color filter140 a prior to exiting the device resulting in external light emission210 a. Similarly, internal light emission 220 c passes through colorfilter 140 c prior to exiting the device resulting in external lightemission 210 c. Color filters 140 a and 140 c are preferably organiclayers as described previously.

The pixels are constructed over substrate 100. Light can exit the deviceby passing through substrate 100 for the case of the bottom emittingdevice, as shown. First electrodes 110 a, 110 b, 110 c, and 110 d arearranged to transmit light and are preferably constructed of aconductive transparent material such as previously described. Secondelectrode 130 is preferably constructed of a reflective conductivematerial such as previously described in order to achieve the desiredlight absorption or reflection properties and conductivity properties.

Yet another alternate four pixel embodiment can be achieved by providinga fourth pixel to the second embodiment of this invention. In thismanner, the fourth pixel emits a color between that of the first andsecond pixels. As such, a common first light emitting layer would beprovided over the first, second, third, and fourth pixels, while thesecond light emitting layer would be provided only over the third pixel.In this alternate embodiment case, the first and second pixels havecolor filters, while the third and fourth pixels have no color filters.

FIG. 9 shows an embodiment of a multicolor OLED display including fivepixels that produce different colored light emission. For example, pixel11 a preferably produces red light, pixel 11 c preferably produces greenlight, and pixel 11 e preferably produces blue light. Pixel 11 bpreferably produces light having a color between that of the red lightof pixel 11 a and the green light of pixel 11 c. Pixel 11 d preferablyproduces light having a color between that of the blue light of pixel 11e and the green light of pixel 11 c. These pixels can be arranged ingroups, such as pixel group 10. Although it is shown that each pixelgroup includes each of the differently colored pixels, the presentinvention is not limited to this case. Instead, some colored pixels canbe present in greater number than other colored pixels. For example,there can be twice as many red pixels as there are yellow pixels. Assuch, each pixel group does not have to contain a pixel having everycolor.

FIG. 10 shows a top side view of pixels 11 a, 11 b, 11 c, 11 d, and 11 eaccording to the fourth embodiment of the present invention. In apassive matrix configuration, these pixels can be addressed by providinga matrix of orthogonal electrodes such as first electrodes 110 a, 110 b,110 c, 110 d, and 110 e and second electrode 130. That is pixel 11 a isconstructed from first electrode 110 a and second electrode 130, pixel11 b is constructed from first electrode 110 b and second electrode 130,pixel 11 c is constructed from first electrode 110 c and secondelectrode 130, pixel 11 d is constructed from first electrode 110 d andsecond electrode 130, and pixel 11 e is constructed from first electrode110 e and second electrode 130. In this configuration, all pixels in acolumn share the same first electrode and all pixels in a row share thesame second electrode. As such these pixels are arranged into a stripepattern. However, the present invention is not limited to thisarrangement and other arrangements such as delta pattern arrangementsand quad arrangements can be applied by one skilled in the art.Furthermore, the present invention is not limited to the passive matrixconfiguration and an active matrix driving scheme can be applied by oneskilled in the art.

According to the present invention, light emitting layer 123 a isprovided for pixels 11 a, 11 b, and 11 c so as to be common betweenthese pixels. This requires light emitting layer 123 a to be preciselyaligned or patterned to these pixels. Light emitting layer 123 c isprovided for all pixels, and therefore requires no precise alignment orpatterning step. In this manner, the number of precision aligneddepositions required to form these five differently colored pixels isreduced from five to one. Light emitting layers 123 a and 123 c can beformed as previously described. Light emitting layer 123 a can becontinuously formed between pixels 11 a, 11 b, and 11 c as shown. Thiscan be achieved, for example, by using a single opening in the shadowmask to deposit the entire layer. Such a continuous arrangement ispreferred to reduce surface area allocated for alignment tolerances inthe manufacturing process. To facilitate such a continuous arrangement,the pixels, which share the same light emitting layer, are preferablydisposed to be adjacent to one and other. For example, pixel 11 b isadjacent to pixel 11 a and pixel 11 c as shown. The present invention,however, is not limited to this preferred embodiment and alternateembodiments where the light emitting layer is discontinuous between thetwo pixels or the two pixels are spaced apart are possible. Suchalternate embodiments are still advantageous in that the number ofprecision aligned depositions is reduced.

Light emitting layer 123 a is preferably arranged to emit light having aspectrum corresponding to a color between red and green as describedpreviously, and produces light having spectral components correspondingto the desired colors of pixels 11 a, 11 b, and 11 c. This can beachieved by forming a light emitting layer of materials that emit a widespectrum of light in the red to green wavelengths. As such, thisunfiltered spectra emission is preferably used for pixel 11 b. Lightemitting layer 123 c is preferably arranged to emit light having aspectrum corresponding to a color between blue and green as describedpreviously, and produces light having spectral components correspondingto the desired colors of pixels 11 d and 11 e. This can be achieved byforming a light emitting layer of materials that emit a wide spectrum oflight in the blue to green wavelengths. As such, this unfiltered spectraemission is preferably used for pixel 11 d. Although light emittinglayers 123 a and 123 c are overlapped for pixels 11 a, 11 b, and 11 c,the combination of light emitting layers 123 a and 123 c is arranged soas to produce light having mostly spectral components corresponding tothe desired color of pixels 11 a, 11 b, and 11 c. In order to achievethe red color desired for pixel 11 a, color filter 140 a is formed inthe path of the light emission between the pixel and the viewer in pixel11 a to absorb undesired spectral components for pixel 11 a and pass thedesired spectral components corresponding to the desired red color. Inorder to achieve the green color desired for pixel 11 c, color filter140 c is formed in the path of the light emission between the pixel andthe viewer in pixel 11 c to absorb undesired spectral components forpixel 11 c and pass the desired spectral components corresponding to thedesired green color. In order to achieve the blue color desired forpixel 11 e, color filter 140 e is formed in the path of the lightemission between the pixel and the viewer in pixel 11 e to absorbundesired spectral components for pixel 11 e and pass the desiredspectral components corresponding to the desired blue color. Amulticolor OLED display made in this manner can have higher powerefficiency. The high efficiency unfiltered wide emission spectrum usedin pixel 11 b or pixel 11 d can be used frequently to replace either thelower efficiency red, blue or green pixels to produce within gamutcolors, as is known in the art.

An alternate five pixel embodiment can be achieved whereby pixel 11 aproduces blue light, pixel 11 c produces green light, and pixel 11 eproduces red light. Pixel 11 b produces light having a color betweenthat of the blue light of pixel 11 a and the green light of pixel 11 c.Pixel 11 d produces light having a color between that of the red lightof pixel 11 e and the green light of pixel 11 c. Light emitting layer123 a is preferably arranged to emit light having a spectrumcorresponding to a color between blue and green as described previously,and produces light having spectral components corresponding to thedesired colors of pixels 11 a, 11 b, and 11 c. This can be achieved byforming a light emitting layer of materials that emit a wide spectrum oflight in the blue to green wavelengths. As such, this unfiltered spectraemission is preferably used for pixel 11 b. Light emitting layer 123 cis preferably arranged to emit light having a spectrum corresponding toa color between red and green as described previously, and produceslight having spectral components corresponding to the desired colors ofpixels 11 d and 11 e. This can be achieved by forming a light emittinglayer of materials that emit a wide spectrum of light in the red togreen wavelengths. As such, this unfiltered spectra emission ispreferably used for pixel 11 d. Although light emitting layers 123 a and123 c are overlapped for pixels 11 a, 11 b, and 11 c, the combination oflight emitting layers 123 a and 123 c is arranged so as to produce lighthaving mostly spectral components corresponding to the desired color ofpixels 11 a, 11 b, and 11 c. In order to achieve the blue color desiredfor pixel 11 a, color filter 140 a is formed in the path of the lightemission between the pixel and the viewer in pixel 11 a to absorbundesired spectral components for pixel 11 a and pass the desiredspectral components corresponding to the desired blue color. In order toachieve the green color desired for pixel 11 c, color filter 140 c isformed in the path of the light emission between the pixel and theviewer in pixel 11 c to absorb undesired spectral components for pixel11 c and pass the desired spectral components corresponding to thedesired green color. In order to achieve the red color desired for pixel11 e, color filter 140 e is formed in the path of the light emissionbetween the pixel and the viewer in pixel 11 e to absorb undesiredspectral components for pixel 11 e and pass the desired spectralcomponents corresponding to the desired red color.

Yet another alternate five pixel embodiment can be achieved by providinga fourth pixel and a fifth pixel to the second embodiment of thisinvention. In this manner, the fourth pixel emits a color between thatof the first and second pixels, and the fifth pixel emits a colorbetween that of the third and fifth pixels. As such, a common firstlight emitting layer would be provided over all pixels, while the secondlight emitting layer would be provided only over the third and fifthpixels. In this alternate embodiment case, the first, second, and thirdpixels have color filters, while the fourth and fifth pixels have nocolor filters.

FIG. 11 shows a cross sectional view of the device of FIG. 10 takenalong line 11-11′. FIG. 11 shows that pixels 11 a, 11 b, 11 c, 11 d, and11 e produce internal light emission 220 a, 220 b, 220 c, 220 d, and 220e, respectively. Internal light emission 220 b and 220 d exit the devicewithout filtration to become external light emission 210 b and 210 d.Internal light emission 220 a passes through color filter 140 a prior toexiting the device resulting in external light emission 210 a. Internallight emission 220 c passes through color filter 140 c prior to exitingthe device resulting in external light emission 210 c. Similarly,internal light emission 220 e passes through color filter 140 e prior toexiting the device resulting in external light emission 210 e. Colorfilters 140 a, 140 c, and 140 e are preferably organic layers aspreviously described.

The pixels are constructed over substrate 100. Light can exit the deviceby passing through substrate 100 for the case of the bottom emittingdevice, as shown. First electrodes 110 a, 110 b, 110 c, 110 d, and 110 eare arranged to transmit light and are preferably constructed of aconductive transparent material such as previously described. Secondelectrode 130 is preferably constructed of a reflective conductivematerial such as previously described in order to achieve the desiredlight absorption or reflection properties and conductivity properties.

Although not always necessary, it is often useful that a hole-injectinglayer (not shown) be formed and disposed over first electrodes 110 a,110 b, 110 c, 110 d, and 110 e. The hole-injecting material can serve toimprove the film formation property of subsequent organic layers and tofacilitate injection of holes into the hole-transporting layer. Suitablematerials for use in the hole-injecting layer include, but are notlimited to, porphyrinic compounds as described in U.S. Pat. No.4,720,432, plasma-deposited fluorocarbon polymers as described in U.S.Pat. No. 6,208,075, and inorganic oxides including vanadium oxide(VO_(x)), molybdenum oxide (MoO_(x)), and nickel oxide (NiO_(x)).Alternative hole-injecting materials reportedly useful in organic ELdevices are described in EP 0 891 121 A1 and EP 1 029 909 A1.

Although not always necessary, it is often useful that ahole-transporting layer 122 be formed and disposed over electrodes 110a, 110 b, 110 c, 110 d, and 110 e. Hole-transporting materials useful inhole-transporting layer 122 are well known to include compounds such asan aromatic tertiary amine, where the latter is understood to be acompound containing at least one trivalent nitrogen atom that is bondedonly to carbon atoms, at least one of which is a member of an aromaticring. In one form the aromatic tertiary amine can be an arylamine, suchas a monoarylamine, diarylamine, triarylamine, or a polymeric arylamine.Exemplary monomeric triarylamines are illustrated by Klupfel, et al. inU.S. Pat. No. 3,180,730. Other suitable triarylamines substituted withone or more vinyl radicals or at least one active hydrogen-containinggroup are disclosed by Brantley, et al. in U.S. Pat. Nos. 3,567,450 and3,658,520.

A more preferred class of aromatic tertiary amines is those that includeat least two aromatic tertiary amine moieties as described in U.S. Pat.Nos. 4,720,432 and 5,061,569. Such compounds include those representedby structural Formula A

wherein:

-   -   Q₁ and Q₂ are independently selected aromatic tertiary amine        moieties; and    -   G is a linking group such as an arylene, cycloalkylene, or        alkylene group of a carbon to carbon bond.

In one embodiment, at least one of Q₁ or Q₂ contains a polycyclic fusedring structure, e.g., a naphthalene moiety. When G is an aryl group, itis conveniently a phenylene, biphenylene, or naphthalene moiety.

A useful class of triarylamines satisfying structural Formula A andcontaining two triarylamine moieties is represented by structuralFormula B

where:

-   -   R₁ and R₂ each independently represent a hydrogen atom, an aryl        group, or an alkyl group or R₁ and R₂ together represent the        atoms completing a cycloalkyl group; and    -   R₃ and R₄ each independently represent an aryl group, which is        in turn substituted with a diaryl substituted amino group, as        indicated by structural Formula C

wherein R₅ and R₆ are independently selected aryl groups. In oneembodiment, at least one of R₅ or R₆ contains a polycyclic fused ringstructure, e.g., a naphthalene.

Another class of aromatic tertiary amines is the tetraaryldiamines.Desirable tetraaryldiamines include two diarylamino groups, such asindicated by Formula C, linked through an arylene group. Usefultetraaryldiamines include those represented by Formula D

wherein:

-   -   each Are is an independently selected arylene group, such as a        phenylene or anthracene moiety;    -   n is an integer of from 1 to 4; and    -   Ar, R₇, R₈, and R₉ are independently selected aryl groups.

In a typical embodiment, at least one of Ar, R₇, R₈, and R₉ is apolycyclic fused ring structure, e.g., a naphthalene.

The various alkyl, alkylene, aryl, and arylene moieties of the foregoingstructural Formulae A, B, C, D, can each in turn be substituted. Typicalsubstituents include alkyl groups, alkoxy groups, aryl groups, aryloxygroups, and halides such as fluoride, chloride, and bromide. The variousalkyl and alkylene moieties typically contain from 1 to about 6 carbonatoms. The cycloalkyl moieties can contain from 3 to about 10 carbonatoms, but typically contain five, six, or seven carbon atoms, e.g.cyclopentyl, cyclohexyl, and cycloheptyl ring structures. The aryl andarylene moieties are typically phenyl and phenylene moieties.

The hole-transporting layer in an OLED device can be formed of a singleor a mixture of aromatic tertiary amine compounds. Specifically, one canemploy a triarylamine, such as a triarylamine satisfying the Formula(B), in combination with a tetraaryldiamine, such as indicated byFormula (D). When a triarylamine is employed in combination with atetraaryldiamine, the latter is positioned as a layer interposed betweenthe triarylamine and the electron injecting and transporting layer.Illustrative of useful aromatic tertiary amines are the following:

-   1,1-Bis(4-di-p-tolylaminophenyl)cyclohexane;-   1,1-Bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;-   4,4′-Bis(diphenylamino)quaterphenyl;-   Bis(4-dimethylamino-2-methylphenyl)-phenylmethane;-   Tri(p-tolyl)amine;-   4-(di-p-tolylamino)-4′-[4′-(di-p-tolylamino)-1-styryl]stilbene;-   N,N,N′,N′-Tetra-p-tolyl-4,4′-diaminobiphenyl;-   N,N,N′,N′-Tetraphenyl-4,4′-diaminobiphenyl;-   N-Phenylcarbazole;-   Poly(N-vinylcarbazole);-   N,N′-di-1-naphthalenyl-N,N′-diphenyl-4,4′-diaminobiphenyl;-   4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB);-   4,4′-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl (TNB);-   4,4″-Bis[N-(1-naphthyl)-N-phenylamino]-p-terphenyl;-   4,4′-Bis[N-(2-naphthyl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl;-   1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene;-   4,4′-Bis[N-(9-anthryl)-N-phenylamino]biphenyl;-   4,4″-Bis[N-(1-anthryl)-N-phenylamino]p-terphenyl;-   4,4′-Bis[N-(2-phenanthryl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(2-pyrenyl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(2-perylenyl)-N-phenylamino]biphenyl;-   4,4′-Bis[N-(1-coronenyl)-N-phenylamino]biphenyl;-   2,6-Bis(di-p-tolylamino)naphthalene;-   2,6-Bis[di-(1-naphthyl)amino]naphthalene;-   2,6-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene;-   N,N,N′,N′-Tetra(2-naphthyl)-4,4″-diamino-p-terphenyl;-   4,4′-Bis {N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl;-   4,4′-Bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl;-   2,6-Bis[N,N-di(2-naphthyl)amino]fluorene; and-   1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene.

Another class of useful hole-transporting materials includes polycyclicaromatic compounds as described in EP 1 009 041. In addition, polymerichole-transporting materials can be used such as poly(N-vinylcarbazole)(PVK), polythiophenes, polypyrrole, polyaniline, and copolymers such aspoly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also calledPEDOT/PSS.

Light emitting layers 123 a and 123 c produce light in response tohole-electron recombination and are disposed over hole-transportinglayer 122, although hole-transporting layer 122 is not required for thepractice of this invention. Useful organic light emitting materials arewell known. As more fully described in U.S. Pat. Nos. 4,769,292 and5,935,721, each of the light emitting layers of the organic EL elementincludes a luminescent or fluorescent material where electroluminescenceis produced as a result of electron-hole pair recombination in thisregion. Although light emitting layers can be comprised of a singlematerial, they more commonly include a host material doped with a guestcompound or dopant where light emission comes primarily from the dopant.The practice of this invention concerns such host/dopant light emittinglayers and OLED devices. Light emitting layer 123 a includes a firsthost, and light emitting layer 123 c includes a second host. Any of thehosts can be the same material. Any of the hosts can comprise a singlehost material or a mixture of host materials. The dopant is selected toproduce colored light having a particular spectrum. The dopant istypically chosen from highly fluorescent dyes, and is typically coatedas 0.01 to 10% by weight into the host material. Light emitting layer123 a includes a light emitting material of the first color, e.g. ayellow-orange or red-orange light emitting material. Light emittinglayer 123 c includes a light emitting material of the second color, e.g.a blue or blue-green light emitting material. The practice of thisinvention is not restricted to this ordering of layers. For instance,light emitting layer 123 a can include a blue or blue-green lightemitting material, and light emitting layer 123 c can include a red,red-orange, or yellow-orange light emitting material. The host materialsin the light emitting layers can be an electron-transporting material, ahole-transporting material, or another material that supportshole-electron recombination. The dopant is typically chosen from highlyfluorescent dyes, but phosphorescent compounds, e.g., transition metalcomplexes as described in WO 98/55561, WO 00/18851, WO 00/57676, and WO00/70655 are also useful.

The host and emitting materials can be small nonpolymeric molecules orpolymeric materials including polyfluorenes and polyvinylarylenes, e.g.,poly(p-phenylenevinylene), PPV. When the host is a polymer, smallmolecule emitting materials can be molecularly dispersed into apolymeric host, or the emitting materials can be added by copolymerizinga minor constituent into a host polymer.

Desirable host materials are capable of forming a continuous film. Thelight emitting layer can contain more than one host material in order toimprove the device's film morphology, electrical properties, lightemission efficiency, and lifetime. The light emitting layer can containa first host material that has effective hole-transporting properties,and a second host material that has effective electron-transportingproperties.

An important relationship for choosing a dye as a dopant is the value ofthe optical bandgap, which is defined the energy difference between theemissive excited state and the ground state of the molecule and isapproximately equal to the energy difference between the lowestunoccupied molecular orbital and the highest occupied molecular orbitalof the molecule. For efficient energy transfer from the host material tothe dopant molecule, or to prevent back-transfer of energy from thedopant to the host, a necessary condition is that the band gap of thedopant be smaller than that of the host material.

Host and emitting molecules known to be of use include, but are notlimited to, those disclosed in U.S. Pat. Nos. 4,768,292, 5,141,671,5,150,006, 5,151,629, 5,294,870, 5,405,709, 5,484,922, 5,593,788,5,645,948, 5,683,823, 5,755,999, 5,928,802, 5,935,720, 5,935,721,6,020,078, and 6,534,199.

Other organic emissive materials can be polymeric substances, e.g.polyphenylenevinylene derivatives, dialkoxy-polyphenylenevinylenes,poly-para-phenylene derivatives, and polyfluorene derivatives, as taughtby Wolk, et al. in commonly assigned U.S. Pat. No. 6,194,119 andreferences cited therein.

Suitable host materials for phosphorescent emitters (including materialsthat emit from a triplet excited state, i.e. so-called “tripletemitters”) should be selected so that the triplet exciton can betransferred efficiently from the host material to the phosphorescentmaterial. For this transfer to occur, it is a highly desirable conditionthat the excited state energy of the phosphorescent material be lowerthan the difference in energy between the lowest triplet state and theground state of the host. However, the band gap of the host should notbe chosen so large as to cause an unacceptable increase in the drivevoltage of the OLED. Suitable host materials are described in WO00/70655 A2; 01/39234 A2; 01/93642 A1; 02/074015 A2; 02/15645 A1, andU.S. Patent Application Publication 2002/0117662 A1. Suitable hostsinclude certain aryl amines, triazoles, indoles and carbazole compounds.Examples of desirable hosts are 4,4′-N,N′-dicarbazole-biphenyl (CBP),2,2′-dimethyl-4,4′-(N,N′-dicarbazole)biphenyl,m-(N,N′-dicarbazole)benzene, and poly(N-vinylcarbazole), including theirderivatives.

In addition to suitable hosts, an OLED device employing a phosphorescentmaterial often requires at least one exciton- or hole-blocking layer tohelp confine the excitons or electron-hole recombination centers to thelight emitting layer comprising the host and phosphorescent material. Inone embodiment, such a blocking layer would be placed between aphosphorescent light emitting layer and the cathode, and in contact withthe phosphorescent light emitting layer. The ionization potential of theblocking layer should be such that there is an energy barrier for holemigration from the host into the electron-transporting layer (or themetal-doped organic layer), while the electron affinity should be suchthat electrons pass more readily from the electron-transporting layer(or the metal-doped organic layer) into the light emitting layercomprising host and phosphorescent material. It is further desired, butnot absolutely required, that the triplet energy of the blockingmaterial be greater than that of the phosphorescent material. Suitablehole-blocking materials are described in WO 00/70655A2 and WO 01/93642A1. Two examples of useful materials are bathocuproine (BCP) andbis(2-methyl-8-quinolinolato)(4-phenylphenolato)-Aluminum(III) (BAlQ).Metal complexes other than Balq are also known to block holes andexcitons as described in U.S. Patent Application Publication2003/0068528 A1. U.S. Patent Application Publication 2003/0175553 A1describes the use of fac-tris(1-phenylpyrazolato-N,C²)iridium(III)(Irppz) in an electron/exciton blocking layer.

Light emitting layer 123 a includes a host material, or mixture ofhosts, and a light emitting material. In one embodiment, the hostmaterial is one or more electron-transporting materials or one or moretetracene derivatives. Electron-transporting materials useful as hostmaterials including metal complexes of 8-hydroxyquinoline and similarderivatives (Formula E) constitute one class of host compounds useful inlight emitting layer 123 a

wherein:

-   -   M represents a metal;    -   n is an integer of from 1 to 3; and    -   Z independently in each occurrence represents the atoms        completing a nucleus having at least two fused aromatic rings.

From the foregoing it is apparent that the metal can be monovalent,divalent, or trivalent metal. The metal can, for example, be an alkalimetal, such as lithium, sodium, or potassium; an alkaline earth metal,such as magnesium or calcium; or an earth metal, such as boron oraluminum. Generally, any monovalent, divalent, or trivalent metal knownto be a useful chelating metal can be employed.

Z completes a heterocyclic nucleus containing at least two fusedaromatic rings, at least one of which is an azole or azine ring.Additional rings, including both aliphatic and aromatic rings, can befused with the two required rings, if required. To avoid addingmolecular bulk without improving on function the number of ring atoms istypically maintained at 18 or less.

Illustrative of useful chelated oxinoid compounds are the following:

-   -   CO-1: Aluminum trisoxine[alias,        tris(8-quinolinolato)aluminum(III)];    -   CO-2: Magnesium bisoxine[alias,        bis(8-quinolinolato)magnesium(II)];    -   CO-3: Bis[benzo{f}-8-quinolinolato]zinc (II);    -   CO-4:        Bis(2-methyl-8-quinolinolato)aluminum(III)-μ-oxo-bis(2-methyl-8-quinolinolato)aluminum(III);    -   CO-5: Indium trisoxine[alias, tris(8-quinolinolato)indium];    -   CO-6: Aluminum tris(5-methyloxine) [alias,        tris(5-methyl-8-quinolinolato)aluminum(III)];    -   CO-7: Lithium oxine[alias, (8-quinolinolato)lithium(I)];    -   CO-8: Gallium oxine [alias, tris(8-quinolinolato)gallium(III)];        and    -   CO-9: Zirconium oxine[alias,        tetra(8-quinolinolato)zirconium(IV)].

Examples of tetracene derivatives useful as hosts or co-hosts in lightemitting layer 123 a are:

wherein R₁-R₆ represent one or more substituents on each ring and whereeach substituent is individually selected from one of the following:

-   -   Category 1: hydrogen, or alkyl of from 1 to 24 carbon atoms;    -   Category 2: aryl or substituted aryl of from 5 to 20 carbon        atoms;    -   Category 3: hydrocarbon containing 4 to 24 carbon atoms,        completing a fused aromatic ring or ring system;    -   Category 4: heteroaryl or substituted heteroaryl of from 5 to 24        carbon atoms such as thiazolyl, furyl, thienyl, pyridyl,        quinolinyl or other heterocyclic systems, which are bonded via a        single bond, or complete a fused heteroaromatic ring system;    -   Category 5: alkoxylamino, alkylamino, or arylamino of from 1 to        24 carbon atoms; or    -   Category 6: fluoro, chloro, bromo or cyano.

In a preferred embodiment, the host material can include a mixture ofone or more tetracene derivatives, and one or more electron-transportingmaterials.

In the preferred embodiment, the light emitting material in lightemitting layer 123 a has a peak emission in the yellow-orange portion ofthe visible spectrum, and can include a yellow-orange light emittingcompound of the following structures:

wherein A₁-A₆ represent one or more substituents on each ring and whereeach substituent is individually selected from one of the following:

-   -   Category 1: hydrogen, or alkyl of from 1 to 24 carbon atoms;    -   Category 2: aryl or substituted aryl of from 5 to 20 carbon        atoms;    -   Category 3: hydrocarbon containing 4 to 24 carbon atoms,        completing a fused aromatic ring or ring system;    -   Category 4: heteroaryl or substituted heteroaryl of from 5 to 24        carbon atoms such as thiazolyl, furyl, thienyl, pyridyl,        quinolinyl or other heterocyclic systems, which are bonded via a        single bond, or complete a fused heteroaromatic ring system;    -   Category 5: alkoxylamino, alkylamino, or arylamino of from 1 to        24 carbon atoms; or    -   Category 6: fluoro, chloro, bromo or cyano.

Examples of particularly useful yellow-orange dopants for use in lightemitting layer 123 a include 5,6,11,12-tetraphenylnaphthacene (P3);6,11-diphenyl-5,12-bis(4-(6-methyl-benzothiazol-2-yl)phenyl)naphthacene(P4); 5,6,11,12-tetra(2-naphthyl)naphthacene (P5); and compounds L49 andL50, the formulas of which are shown below:

A suitable yellow-orange dopant can also be a mixture of compounds thatwould also be yellow-orange dopants individually.

In another useful embodiment, the light emitting material in lightemitting layer 123 c has a peak emission in the yellow-orange portion ofthe visible spectrum and contains yellow-orange light emitting materialsand hosts as described above. In yet another useful embodiment, lightemitting layer 123 c has a peak emission in the red portion of thevisible spectrum, and can include a red or red-orange light emittingdopant. A suitable light emitting red or red-orange dopant can include adiindenoperylene compound of the following structure:

wherein X₁-X₁₆ are independently selected as hydro or substituents thatprovide red luminescence.

A particularly preferred diindenoperylene dopant isdibenzo{[f,f′]-4,4′7,7′-tetraphenyl]diindeno-[1,2,3-cd:1′,2′,3′-lm]perylene (TPDBP, below)

Other red or red-orange dopants useful in the present invention belongto the DCM class of dyes represented by

wherein:

-   -   Y₁-Y₅ represent one or more groups independently selected from        hydro, alkyl, substituted alkyl, aryl, or substituted aryl; and    -   Y₁-Y₅ independently include acyclic groups or are joined        pairwise to form one or more fused rings, provided that Y₃ and        Y₅ do not together form a fused ring.

In a useful and convenient embodiment that provides red-orangeluminescence, Y₁-Y₅ are selected independently from hydro, alkyl andaryl. A preferred DCM dopant is DCJTB shown below.

A useful red or red-orange dopant can also be a mixture of compoundsthat would also be red or red-orange dopants individually.

Light emitting layer 123 c includes a host material, or mixture ofhosts, and a light emitting material. In the preferred embodiment, lightemitting layer 123 c has a peak emission in the blue to blue-greenportion of the visible spectrum. In one embodiment, the host material isone or more anthracene or mono-anthracene derivatives. Derivatives of9,10-di-(2-naphthyl)anthracene (Formula F) constitute one class of hostsuseful in light emitting layer 123 c

wherein:

-   -   R¹, R², R³, R⁴, R⁵, and R⁶ represent one or more substituents on        each ring where each substituent is individually selected from        the following groups:

-   Group 1: hydrogen, or alkyl of from 1 to 24 carbon atoms;

-   Group 2: aryl or substituted aryl of from 5 to 20 carbon atoms;

-   Group 3: carbon atoms from 4 to 24 necessary to complete a fused    aromatic ring of anthracenyl; pyrenyl, or perylenyl;

-   Group 4: heteroaryl or substituted heteroaryl of from 5 to 24 carbon    atoms as necessary to complete a fused heteroaromatic ring of furyl,    thienyl, pyridyl, quinolinyl or other heterocyclic systems;

-   Group 5: alkoxylamino, alkylamino, or arylamino of from 1 to 24    carbon atoms; and

-   Group 6: fluorine, chlorine, bromine or cyano.

Benzazole derivatives (Formula G) constitute another class of hostsuseful in light emitting layer 123 c

wherein:

-   -   n is an integer of 3 to 8;    -   Z is O, NR or S;    -   R′ is hydrogen; alkyl of from 1 to 24 carbon atoms, for example,        propyl, t-butyl, heptyl, and the like; aryl or hetero-atom        substituted aryl of from 5 to 20 carbon atoms for example phenyl        and naphthyl, furyl, thienyl, pyridyl, quinolinyl and other        heterocyclic systems; or halo such as chloro, fluoro; or atoms        necessary to complete a fused aromatic ring; and    -   L is a linkage unit includes alkyl, aryl, substituted alkyl, or        substituted aryl, which conjugately or unconjugately connects        the multiple benzazoles together.

An example of a useful benzazole is 2, 2′,2″-(1,3,5-phenylene)-tris[1-phenyl-1H-benzimidazole].

It has been found in commonly assigned U.S. patent application Ser. No.10/693,121 filed Oct. 24, 2003 by Lelia Cosimbescu, et al., entitled“Electroluminescent Device With Anthracene Derivative Host”, thedisclosure of which is herein incorporated by reference, that certainunsymmetrical anthracenes are extremely useful in OLED devices thatexhibit high efficiencies. These compounds have been found to beparticularly useful in blue light emitting layers of OLED devices thatproduce blue, blue-green, or green light. Blue or blue-green lightemitting layer 123 c can include a mono-anthracene derivative of Formula(I) as a host material

wherein:

-   -   R₁-R₈ are H; and    -   R₉ is a naphthyl group containing no fused rings with aliphatic        carbon ring members; provided that R₉ and R₁₀ are not the same,        and are free of amines and sulfur compounds. Suitably, R₉ is a        substituted naphthyl group with one or more further fused rings        such that it forms a fused aromatic ring system, including a        phenanthryl, pyrenyl, fluoranthene, perylene, or substituted        with one or more substituents including fluorine, cyano group,        hydroxy, alkyl, alkoxy, aryloxy, aryl, a heterocyclic oxy group,        carboxy, trimethylsilyl group, or an unsubstituted naphthyl        group of two fused rings. Conveniently, R₉ is 2-naphthyl, or        1-naphthyl substituted or unsubstituted in the para position;        and    -   R₁₀ is a biphenyl group having no fused rings with aliphatic        carbon ring members. Suitably R₁₀ is a substituted biphenyl        group, such that it forms a fused aromatic ring system including        but not limited to a naphthyl, phenanthryl, perylene, or        substituted with one or more substituents including fluorine,        cyano group, hydroxy, alkyl, alkoxy, aryloxy, aryl, a        heterocyclic oxy group, carboxy, trimethylsilyl group, or an        unsubstituted biphenyl group. Conveniently, R₁₀ is 4-biphenyl,        3-biphenyl unsubstituted or substituted with another phenyl ring        without fused rings to form a terphenyl ring system, or        2-biphenyl. Particularly useful is        9-(2-naphthyl)-10-(4-biphenyl)anthracene.

Some examples of useful mono-anthracene host materials for use in lightemitting layer 123 c include:

Particularly useful is 9-(2-naphthyl)-10-(4-biphenyl)anthracene(Host-1).

In a preferred embodiment, the host material in light emitting layer 123c can include a mixture of one or more anthracene or mono-anthracenederivatives mentioned above, and one or more aromatic amine derivatives.The aromatic amine derivative in light emitting layer 123 c can be anysuch amine that has hole-transporting properties, and can be selectedfrom the same potential hole-transporting materials as inhole-transporting layer 122. Particularly useful is4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB).

In the preferred embodiment, the light emitting material in lightemitting layer 123 c has a peak emission in the blue portion of thevisible spectrum, and can include blue light emitting dopants includingperylene or derivatives thereof, blue-emitting derivatives ofdistyrylbenzene or a distyrylbiphenyl that have one or more aryl aminesubstituents, or a compound of the structure

wherein:

-   -   A and A′ represent independent azine ring systems corresponding        to 6-membered aromatic ring systems containing at least one        nitrogen;    -   (X^(a))_(n) and (X^(b))_(m) represent one or more independently        selected substituents and include acyclic substituents or are        joined to form a ring fused to A or A′;    -   m and n are independently 0 to 4;    -   Z^(a) and Z^(b) are independently selected substituents;    -   1, 2, 3, 4, 1′, 2′, 3′, and 4′ are independently selected as        either carbon or nitrogen atoms; and    -   provided that X^(a), X^(b), Z^(a), and Z^(b), 1, 2, 3, 4, 1′,        2′, 3′, and 4′ are selected to provide blue luminescence.

Some examples of the above class of dopants include the following:

Preferred blue dopants are BEP and tetra-t-butylperylene (TBP). A usefulblue dopant can also be a mixture of compounds that would also be bluedopants individually.

In another preferred embodiment, the light emitting material in lightemitting layer 123 c has a peak emission in the blue-green portion ofthe visible spectrum, and can include blue-green emitting derivatives ofsuch distyrylarenes as distyrylbenzene and distyrylbiphenyl, includingcompounds described in U.S. Pat. No. 5,121,029. Among derivatives ofdistyrylarenes that provide blue or blue-green luminescence,particularly useful are those substituted with diarylamino groups, alsoknown as distyrylamines. Examples includebis[2-[4-[N,N-diarylamino]phenyl]vinyl]-benzenes of the generalstructure N1 shown below:

and bis[2-[4-[N,N-diarylamino]phenyl]vinyl]biphenyls of the generalstructure N2 shown below:

In Formulas N1 and N2, R₁-R₄ can be the same or different, andindividually represent one or more substituents such as alkyl, aryl,fused aryl, halo, or cyano. In a preferred embodiment, R₁-R₄ areindividually alkyl groups, each containing from one to about ten carbonatoms. A particularly useful blue-green dopant of this class is1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (BDTAPVB)

In a useful embodiment of the invention, light emitting layer 123 cincludes a blue-green dopant of Formula (3)

wherein R¹ through R⁴ can be the same or different and individuallyrepresent hydrogen or one or more substituents, for example, alkylgroups, such as methyl groups, alkoxy groups, such as methoxy, arylgroups, such as phenyl, or aryloxy groups, such as phenoxy.

Particularly useful embodiments of the blue-green emissive dopants oflight emitting layer 123 c are shown in Formula (4-1) through Formula(4-5)

In other embodiments of the invention, the light emitting material inlight emitting layer 123 a has a peak emission in the blue or blue-greenportion of the visible spectrum and contains blue or blue-green lightemitting materials and hosts as described above.

Although not always necessary, it is often useful that an organic layeris formed over light emitting layers 123 a and 123 c, wherein theorganic layer includes an electron-transporting material, e.g.electron-transporting layer 124. Preferred electron-transportingmaterials for use in electron-transporting layer 124 are metal chelatedoxinoid compounds, including chelates of oxine itself (also commonlyreferred to as 8-quinolinol or 8-hydroxyquinoline). Such compounds helpto inject and transport electrons and both exhibit high levels ofperformance and are readily fabricated in the form of thin films.Exemplary of contemplated oxinoid compounds are those satisfyingstructural Formula E

wherein:

-   -   M represents a metal;    -   n is an integer of from 1 to 3; and    -   Z independently in each occurrence represents the atoms        completing a nucleus having at least two fused aromatic rings.

From the foregoing it is apparent that the metal can be a monovalent,divalent, or trivalent metal. The metal can, for example, be an alkalimetal, such as lithium, sodium, or potassium; an alkaline earth metal,such as beryllium, magnesium or calcium; or an earth metal, such asboron or aluminum. Generally any monovalent, divalent, or trivalentmetal known to be a useful chelating metal can be employed.

Z completes a heterocyclic nucleus containing at least two fusedaromatic rings, at least one of which is an azole or azine ring.Additional rings, including both aliphatic and aromatic rings, can befused with the two required rings, if required. To avoid addingmolecular bulk without improving on function the number of ring atoms istypically maintained at 18 or less.

Illustrative of useful chelated oxinoid compounds are the following:

-   -   CO-1: Aluminum trisoxine[alias,        tris(8-quinolinolato)aluminum(III)];    -   CO-2: Magnesium bisoxine[alias,        bis(8-quinolinolato)magnesium(II)];    -   CO-3: Bis[benzo{f}-8-quinolinolato]zinc(II);    -   CO-4:        Bis(2-methyl-8-quinolinolato)aluminum(III)-μ-oxo-bis(2-methyl-8-quinolinolato)aluminum(III);    -   CO-5: Indium trisoxine[alias, tris(8-quinolinolato)indium];    -   CO-6: Aluminum tris(5-methyloxine)[alias,        tris(5-methyl-8-quinolinolato)aluminum(III)];    -   CO-7: Lithium oxine[alias, (8-quinolinolato)lithium(I)];    -   CO-8: Gallium oxine[alias, tris(8-quinolinolato)gallium(III)];        and    -   CO-9: Zirconium oxine[alias,        tetra(8-quinolinolato)zirconium(IV)].

Other electron-transporting materials include various butadienederivatives as disclosed in U.S. Pat. No. 4,356,429 and variousheterocyclic optical brighteners as described in U.S. Pat. No.4,539,507. Benzazoles satisfying structural Formula G are also usefulelectron-transporting materials.

Other electron-transporting materials can be polymeric substances, e.g.polyphenylenevinylene derivatives, poly-para-phenylene derivatives,polyfluorene derivatives, polythiophenes, polyacetylenes, and otherconductive polymeric organic materials such as those listed in Handbookof Conductive Molecules and Polymers, Vols. 1-4, H. S. Nalwa, ed., JohnWiley and Sons, Chichester (1997).

An electron-injecting layer (not shown) can also be present between thecathode and the electron-transporting layer. Examples ofelectron-injecting materials include alkali or alkaline earth metals,alkali halide salts, such as LiF mentioned above, or alkali or alkalineearth metal doped organic layers.

Desired organic materials for the hole-transporting layer 122, lightemitting layers 123 a and 123 c, and electron-transporting layer 124 canbe deposited and patterned by any one or more of several methods knownin the art. For example, organic materials can be deposited by thermalevaporation from a heated source and pattern achieved by selectivelyblocking deposition by use of a shadow masking structure. Alternately,the materials can first be deposited onto a donor sheet, which is thenplaced in contact or in proximity to the display substrate and thematerials can be selectively transferred by writing with a laser.Alternately, some materials can be dissolved in a solvent and thenselectively deposited on the substrate in the desired location byplacing droplets of the solution by drop ejecting apparatus such as anink jet head.

The device can further include an encapsulation means (not shown) forpreventing moisture from the environment from degrading the device as isknown in the art. The encapsulation means can be a glass or metal coverhermetically sealed to the substrate or can be a thin film of moistureimpermeable material coated over the pixels. The encapsulation means canfurther include a desiccant for absorbing moisture.

EXAMPLES

The invention and its advantages can be better appreciated by thefollowing inventive and comparative examples. In the following, mixedcompositions are described in terms of percentages or ratios by volume,as are commonly used in the art.

Example 1(Comparative)

A comparative OLED device was constructed in the following manner:

-   -   1. A clean glass substrate was vacuum-deposited with indium tin        oxide (ITO) to form a transparent electrode of 85 nm thickness;    -   2. The above-prepared ITO surface was treated with a plasma        oxygen etch, followed by plasma deposition of a 0.5 nm layer of        a fluorocarbon polymer (CFx) as described in U.S. Pat. No.        6,208,075;    -   3. The above-prepared substrate was further treated by        vacuum-depositing a 240 nm layer of        4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) as a        hole-transporting layer (HTL);    -   4. A coating of 30 nm thickness, composed of 97.5% NPB (as host)        with 2.5% yellow-orange emitting dopant        5,11-bis(biphenyl-4-yl)-6,12-bis(4-tert-butylphenyl)-3,9-di-tert-butylnaphthacene        (Formula L50) were co-evaporatively deposited onto the HTL layer        to form a yellow-orange emitting first light emitting layer;    -   5. A coating of 45 nm thickness, composed of 92%        9-(2-naphthyl)-10-(4-biphenyl)anthracene (Host1), 7% NPB, and 1%        tetra-t-butylperylene (TBP), was co-evaporatively deposited onto        the above substrate to form a blue emitting second light        emitting layer;    -   6. A 10 nm layer of tris(8-quinolinolato)aluminum (III) (ALQ)        was vacuum-deposited onto the above substrate at a coating        station that included a heated graphite boat source to form an        electron-transporting layer;    -   7. A 100 nm cathode layer was deposited onto the        electron-transporting layer. The cathode includes 0.5 nm of LiF        as an electron injection layer followed by 100 nm of aluminum,        to form a cathode layer; and    -   8. The device was then transferred to a dry box for        encapsulation.

Example 2

Example 2 was prepared similar to Example 1, with the exception of theyellow-orange emitting layer, which included tBuDPN co-dopant (FormulaP6). The yellow-orange emitting layer of Example 2 was composed of 78%NPB (as host) with 19.5% tBuDPN (Formula P6) and 2.5% of5,11-bis(biphenyl-4-yl)-6,12-bis(4-tert-butylphenyl)-3,9-di-tert-butylnaphthacene(Formula L50). The blue layer, ETL and cathode layers were the same. Thedevice was then transferred to a dry box for encapsulation.

Example 3

Example 3 was prepared similar to Example 1, with the exception that theyellow-orange light emitting layer was not included, and the HTL layerwas slightly thicker. The blue layer, ETL and cathode layers were thesame. The device was then transferred to a dry box for encapsulation.

Example 4(Inventive)

Example 4 is an example of an OLED display device provided by thisinvention. The OLED devices of Examples 2 and 3 are combined into oneOLED display device in Example 4 to make a multicolor RGB displayaccording to this invention.

TABLE 1 Performance HTL Yellow-Orange EML (30 nm) Blue EML (45 nm) Lum.Eff. Examples NPB (nm) NPB % P6 % L50 % Host1 % NPB % TBP % (cd/A) CIExCIEy 1 240 97.5 0 2.5 92 7 1 12.0 0.32 0.32 2 240 78 19.5 2.5 92 7 116.5 0.43 0.41 3 300 0 0 0 92 7 1 5.2 0.14 0.17

Table 1 shows the device performance of Examples 1 to 3. It shows thedevice structure, luminance efficiency, and CIEx,y chromaticity. Thefirst example is a typical white OLED with effective efficiency anddesirable CIEx,y chromaticity. Example 2 is a yellowish-white OLEDdevice with higher efficiency, and Example 3 is a blue OLED device, withthe same blue EML as in Examples 1 and 2.

FIG. 12 shows the EL spectra of the devices of Examples 1 to 3. The ELspectrum of Example 1 shows a typical white OLED device, withyellow-orange and blue light emitting layers balanced in the appropriateratios to give effective white emission. The CIEx,y chromaticity forthis device was (0.32, 0.32). The EL spectrum of Example 2 shows ayellow-shifted ‘white’ OLED device, with CIEx,y chromaticity of (0.43,0.41). The yellow-orange peak of device 2 has higher intensity than thatof device 1, resulting in higher efficiency. The EL spectrum of Example3 shows a blue OLED device. The blue peak of device 3 has higherintensity than that of devices 1 and 2. Devices 1, 2, and 3 all containthe same blue light emitting layer.

TABLE 2 Red Green Blue RGB Lum. Eff. Lum. Eff. Lum. Eff. Power Examples(cd/A) CIEx CIEy (cd/A) CIEx CIEy (cd/A) CIEx CIEy (mW) 1 2.4 0.64 0.366.1 0.31 0.54 1.3 0.13 0.10 546 2 4.0 0.64 0.36 8.0 0.38 0.55 0.8 0.130.11 580 3 n/a 5.2 0.14 0.17 n/a 4 4.0 0.64 0.36 8.0 0.38 0.55 5.2 0.140.17 314

Table 2 shows the simulated performance of Examples 1 to 4 in amulticolor three pixel RGB display. It shows the luminance efficiencyand CIEx,y chromaticity for the red, green, and blue pixels using atypical set of LCD color filters (except for Example 3, which does notuse color filters). In addition, it gives the predicted average powerconsumption (mW) for an RGB display at the panel luminance level of 180cd/m2, given a typical set of digital pictorial images. The powerconsumption calculation assumes a display size of 2.16″ diagonal, acircular polarizer with 44% transmittance, and a typical set of LCDcolor filters. The first example is a typical white OLED with effectiveefficiency and desirable CIEx,y chromaticity, resulting in a powerconsumption of 546 mW. Although Example 2 has higher efficiency, it doesnot have effective white color resulting in higher power consumption.Example 4 combines the red and green pixels of Example 2 along with theblue pixel of Example 3, according to the first embodiment of thisinvention. Due to the unfiltered high efficiency blue pixel and thehigher efficiency red and green pixels, the power consumption is muchlower (and therefore the power efficiency is higher) than either Example1 or 2. Further advantages in power efficiency would be obtained if afour pixel or five pixel multicolor OLED display were constructedaccording to other embodiments in the present invention. For instance,if a fourth unfiltered pixel were provided using the high efficiencyyellow-orange emission from the device of Example 2 according to thethird embodiment of this invention, then a further reduction in powerconsumption would be obtained.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST 10 pixel group 11a pixel 11b pixel 11c pixel 11d pixel 11epixel 100 substrate 110a first electrode 110b first electrode 110c firstelectrode 110d first electrode 110e first electrode 122hole-transporting layer 123a light emitting layer 123c light emittinglayer 124 electron-transporting layer 130 second electrode 140a colorfilter 140b color filter 140c color filter 140e color filter 210aexternal light emission 210b external light emission 210c external lightemission 210d external light emission 210e external light emission 220ainternal light emission 220b internal light emission 220c internal lightemission 220d internal light emission 220e internal light emission

1. An OLED display having at least first, second, and third differentlycolored pixels, comprising: a) a first light emitting layer providedcontinuously over a substrate for the first and second pixels but notthe third pixel and a second light emitting layer provided continuouslyover the substrate for the first, second, and third pixels, wherein thefirst and second light emitting layers produce light having differentspectra, and wherein the light produced by overlapping the first andsecond light emitting layers has substantial spectral componentscorresponding to the light output desired for the first and secondpixels, and the light produced by the second light emitting layer hassubstantial spectral components corresponding to the light outputdesired for the third pixel; and b) first and second color filters inoperative relationship with the first and second pixels.
 2. The OLEDdisplay according to claim 1 wherein the light spectrum produced by thefirst light emitting layer has substantial spectral componentscorresponding to yellow-orange light, and wherein the light spectrumproduced by the second light emitting layer has substantial spectralcomponents corresponding to blue light.
 3. The OLED display according toclaim 2 wherein the first color filter passes red light and absorbslight of other colors, and the second color filter passes green lightand absorbs light of other colors.
 4. The OLED display according toclaim 1 wherein the light spectrum produced by overlapping the first andsecond light emitting layers has substantial spectral componentscorresponding to yellow-orange light.
 5. The OLED display according toclaim 1 wherein the light spectrum produced by the first light emittinglayer has substantial spectral components corresponding to blue-greenlight, and wherein the light spectrum produced by the second lightemitting layer has substantial spectral components corresponding to redlight.
 6. The OLED display according to claim 5 wherein the lightspectrum produced by overlapping the first and second light emittinglayers has substantial spectral components corresponding to blue-greenlight.
 7. The OLED display according to claim 5 wherein the first colorfilter passes blue light and absorbs light of other colors, and thesecond color filter passes green light and absorbs light of othercolors.
 8. The OLED display according to claim 1 wherein the first andsecond light emitting layers are provided over the substrate for afourth pixel, and wherein the light produced by overlapping the firstand second light emitting layers has substantial spectral componentscorresponding to the light output desired for the first, second, andfourth pixels.
 9. The OLED display according to claim 8 wherein thelight spectrum produced by the first light emitting layer hassubstantial spectral components corresponding to yellow-orange light,and the light spectrum produced by the second light emitting layer hassubstantial spectral components corresponding to blue light.
 10. TheOLED display according to claim 8 wherein the light spectrum produced byoverlapping the first and second light emitting layers has substantialspectral components corresponding to yellow-orange light.
 11. The OLEDdisplay according to claim 8 wherein the first color filter passes redlight and absorbs light of other colors, and the second color filterpasses green light and absorbs light of other colors.
 12. The OLEDdisplay according to claim 8 wherein the second pixel is adjacent to thefirst and fourth pixels, or the first pixel is adjacent to the secondand fourth pixels, or the fourth pixel is adjacent to the first andsecond pixels.
 13. The OLED display according to claim 12 wherein thefirst light emitting layer is continuously formed to correspond to thefirst, second, and fourth pixels.
 14. The OLED display according toclaim 8 wherein the second light emitting layer is provided over thesubstrate for a fifth pixel, and wherein the light produced by thesecond light emitting layer has substantial spectral componentscorresponding to the light output desired for the third and fifthpixels.
 15. The OLED display according to claim 14 wherein the lightspectrum produced by the first light emitting layer has substantialspectral components corresponding to yellow-orange light, and the lightspectrum produced by the second light emitting layer has substantialspectral components corresponding to blue-green light.
 16. The OLEDdisplay according to claim 14 wherein the light spectrum produced byoverlapping the first and second light emitting layers has substantialspectral components corresponding to yellow-orange light.
 17. The OLEDdisplay according to claim 14 wherein the first color filter passes redlight and absorbs light of other colors, the second color filter passesgreen light and absorbs light of other colors, and a third color filteris provided over the third pixel that passes blue light and absorbslight of other colors.
 18. The OLED display according to claim 14wherein the second pixel is adjacent to the first and fourth pixels, orthe first pixel is adjacent to the second and fourth pixels, or thefourth pixel is adjacent to the first and second pixels.
 19. An OLEDdisplay having at least first, second, and third differently coloredpixels, comprising: a) a first light emitting layer providedcontinuously over a substrate for the first, second, and third pixelsand a second light emitting layer provided over the substrate for thethird pixel but not the first or second pixel, wherein the first andsecond light emitting layers produce light having different spectra, andwherein the light produced by overlapping the first and second lightemitting layers has substantial spectral components corresponding to thelight output desired for the third pixel; and b) first and second colorfilters in operative relationship with the first and second pixels. 20.The OLED display according to claim 19 wherein the light spectrumproduced by the first light emitting layer has substantial spectralcomponents corresponding to yellow-orange light, and the light spectrumproduced by the second light emitting layer has substantial spectralcomponents corresponding to blue light.
 21. The OLED display accordingto claim 19 wherein the light spectrum produced by overlapping the firstand second light emitting layers has substantial spectral componentscorresponding to blue light.
 22. The OLED display according to claim 19wherein the first color filter passes red light and absorbs light ofother colors, and the second color filter passes green light and absorbslight of other colors.
 23. The OLED display according to claim 19wherein the first light emitting layer is provided over the substratefor a fourth pixel, and wherein the light produced by the first lightemitting layer has substantial spectral components corresponding to thelight output desired for the first, second, and fourth pixels.
 24. TheOLED display according to claim 23 wherein the light spectrum producedby the first light emitting layer has substantial spectral componentscorresponding to yellow-orange light, and the light spectrum produced bythe second light emitting layer has substantial spectral componentscorresponding to blue light.
 25. The OLED display according to claim 24wherein the first color filter passes red light and absorbs light ofother colors, and the second color filter passes green light and absorbslight of other colors.
 26. The OLED display according to claim 23wherein the light spectrum produced by overlapping the first and secondlight emitting layers has substantial spectral components correspondingto blue light.
 27. The OLED display according to claim 23 wherein thefirst and second light emitting layers are provided over the substratefor a fifth pixel, and wherein the light produced by overlapping thefirst and second light emitting layers has substantial spectralcomponents corresponding to the light output desired for the third andfifth pixels.
 28. The OLED display according to claim 27 wherein thelight spectrum produced by the first light emitting layer hassubstantial spectral components corresponding to yellow-orange light,and the light spectrum produced by the second light emitting layer hassubstantial spectral components corresponding to blue-green light. 29.The OLED display according to claim 27 wherein the light spectrumproduced by overlapping the first and second light emitting layers hassubstantial spectral components corresponding to blue-green light. 30.The OLED display according to claim 27 wherein the first color filterpasses red light and absorbs light of other colors, the second colorfilter passes green light and absorbs light of other colors, and a thirdcolor filter is provided over the third pixel that passes blue light andabsorbs light of other colors.
 31. The OLED display according to claim27 wherein the third pixel is adjacent to the fifth pixel.